Motor vehicles are supported by inflatable tires having a desired inflation pressure. Improper inflation of a tire can lead to poor gas mileage and increased tire wear. Maintaining tire inflation within an acceptable range can alleviate these issues. To do so however, requires frequent measuring of tire pressure and evaluation of whether that pressure lies within an acceptable range. Moreover, tire pressure will also vary according to temperature and vehicle load.
Systems that automatically monitor pressure and provide an indication to the vehicle operator when the fluid (typically air) within the pressure vessel (e.g., the tire) reaches a condition of improper inflation typically include a pressure sensor in communication with an external receiver capable of interfacing with the vehicle operator. These systems are typically a collection of remote electronic circuits for both sensing the tire pressure and communicating the pressure information to a separate receiver, which in-turn interfaces with the vehicle operator. The actual pressure sensor may be located external to the tire, for example on or in the valve stem of the wheel. The sensor may also be located directly within the mounted wheel/tire assembly. Because the sensors are located in remote areas of the vehicle, these systems are required to operate under their own power (e.g., battery power).
The communication link between the sensor and the external receiver may be wireless, with radio frequency signals and/or infrared or optical signals being the most common forms. However, the utility of wireless communication in these systems is severely limited due to reliance on battery power. Because batteries in these systems are not readily replaced, such systems can only consume an amount of power that allows the battery to last over the useful lifetime of the vehicle. Battery replacement is not available for a variety of reasons including the corrosive environment within an inflated tire.
The environment within an inflated tire is corrosive due to the moisture content and various other corrosive materials present in the tires themselves. Temperature extremes that range from sub-zero to several hundred degrees, along with the constant forces, vibrations and shocks routinely at work add to the inhospitable nature of this environment. To combat these forces acting upon in-wheel sensors, components are typically well secured and sealed to mitigate external effects, and to prevent damage to the apparatus. While this approach serves a protective function, it makes battery replacement difficult if not impossible without destroying the apparatus itself.
Thus, to provide the needed longevity, a relatively large battery must be used. This in turn results in a greater force acting on the battery due to the forces of the rotating tire, in combination with the increase in mass and expense of a larger battery. In addition, the unit must be replaced as a whole and so cannot be serviced piecemeal. Accordingly, a tire pressure sensing and transmitting assembly having a replaceable battery would be of great benefit.
Disclosed herein is a pressure transducer assembly mountable in an interior of a pressure vessel (e.g., a tire mounted on a wheel) for sensing a pressure of a fluid in the container comprising: a sensor housing having a first compartment in fluid communication with the fluid; a second compartment separated from the first compartment by a divider slideably engaged with and removable from the sensor housing; the divider having disposed thereon a circuitry; the circuitry including a pressure transducer in fluid communication with the first compartment, and a transmission circuit coupled to the pressure transducer for transmitting a signal responsive to the internal pressure, to a remote location; a removable power source coupled to the circuitry contained entirely within the second compartment; and a cover sealingly engaged with the housing and the divider such that the second compartment is not in fluid communication with the first compartment.
Also disclosed is a method of sensing a pressure of a fluid within a tire and communicating the pressure to an external receiver located in a remote location, comprising: disposing a pressure transducer assembly within the pressure vessel in communication with the fluid; sensing the pressure of the fluid; and transmitting a signal responsive to the pressure to the external receiver located in the remote location; the pressure transducer assembly comprising: a sensor housing having a first compartment in fluid communication with the fluid; a second compartment separated from the first compartment by a divider slideably engaged with and removable from the sensor housing; the divider having disposed thereon a circuitry; the circuitry including a pressure transducer in fluid communication with the first compartment, and a transmission circuit coupled to the pressure transducer for transmitting the signal responsive to the pressure to the external receiver located in the remote location; a removable power source coupled to the circuitry contained entirely within the second compartment; and a cover sealing engaged with the housing and the divider such that the second compartment is not in fluid communication with the first compartment.
The above described and other features are exemplified by the following figures and detailed description.